Beginning no earlier than day 28 after the second PBSCT, patients undergo local radiotherapy to the primary site and sites that are positive by meta-iodobenzylguanidine scan after induction twice a day for 7 days (or once a day for 12 days if twice daily dosing is not possible). Beginning on day 90 after the second PBSCT, patients receive oral isotretinoin twice a day for 2 weeks. Treatment repeats every 4 weeks for 6 courses in the absence of disease progression or unacceptable toxicity.